1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device including a platinum layer, and particularly to a method for cleaning the semiconductor device using plasma.
2. Description of the Related Art
In recent years, platinum (Pt) has been used in many semiconductor devices as a material of electrodes in a DRAM (Dynamic Random Access Memory) or FeRAM (Ferroelectric Random Access Memory). As the integration density of the DRAM or FeRAM has become higher, the demand for finely etching the platinum layer has increased.
A thin film made of material having a low vapor pressure, such as platinum, is generally etched by physical etching in the following manner. First, plasma is generated in a process chamber, for example. Then, bias power is applied to an electrode on which a substrate to be processed is placed, so that an electric field is generated in the plasma. The electric field attracts ions in the plasma to the surface of the substrate, thereby etching the substrate.
However, in the physical etching generally employed to etch a thin film made of material having a low vapor pressure, such as platinum, the etching product is not volatilized. Therefore, minute platinum particles having a diameter of several nanometers adhere to the surface of the substrate to be processed. The adhesion of the platinum etching product to the surface of the substrate deteriorates the electrical characteristics of the semiconductor device including the substrate.
In connection with this matter, a technique for carrying out etching without adhesion of the platinum etching product has been disclosed (PCT National Publication No. 2002-537645).